The present application relates to a secondary battery including a cathode, an anode, and a nonaqueous electrolytic solution, and a battery pack, an electric vehicle, a energy storage system, an electric power tool, and an electronic unit each using the secondary battery.
In recent years, various electronic units such as cellular phones and personal digital assistants (PDAs) have been widely used, and further size and weight reduction and longer life of the electronic units are desired. Accordingly, as power supplies for the electronic units, batteries, in particular, small and lightweight secondary batteries capable of obtaining high energy density have been developed. Recently, other various applications of the secondary batteries, as typified by battery packs removably mounted in electronic units or the like, electric vehicles such as electric cars, energy storage systems such as home energy servers, and electric power tools such as electric drills have been studied.
Secondary batteries obtaining battery capacity with use of various charge-discharge principles have been proposed, and in particular, lithium secondary batteries with use of lithium as an electrode reactant holds great promise, because the secondary batteries are allowed to obtain higher energy density than lead-acid batteries or nickel-cadmium batteries. The lithium secondary batteries include lithium-ion secondary batteries using insertion and extraction of lithium ions and lithium metal secondary batteries using deposition and dissolution of lithium metal.
The secondary battery includes a cathode, an anode, and an electrolytic solution, and the electrolytic solution includes a nonaqueous solvent and an electrolyte salt. As the electrolytic solution functioning as a medium of charge-discharge reaction exerts a large effect on performance of the secondary battery, various compositions of the electrolytic solution have been studied.
More specifically, it is proposed to use a cyclic carbonate having a carbon-carbon double bond (a methylene group) to suppress reductive decomposition reaction of the electrolytic solution (for example, refer to Japanese Unexamined Patent Application Publication No. 2000-058122 and Japanese Unexamined Patent Application Publication (Published Japanese Translation of PCT application) No. 2010-533359). As the cyclic carbonate having a methylene group, 4-methylene-1,3-dioxolane-2-one, 4,4-dimethyl-5-methylene-1,3-dioxolane-2-one, or the like is used.